The present invention relates generally to the field of cement paving. More particularly, the present invention relates to evaluating the surface profile of recently laid cement in real time.
During new construction and during resurfacing, large surfaces are paved with concrete. Once set, the cement cannot be readily reshaped. In a worst case scenario, large cement pours have to be ground because the dried surface is unsatisfactory. These grinding procedures are expensive, time consuming, and labor intensive. This is one reason that pavers, such as paving contractors and departments of transportation, desire a method and system for ascertaining and measuring surface discrepancies in cement when alternate methods of correction are still possible.
Typically, re-surfacing by adding an additional top layer is not possible due to bonding inadequacy. A restriction on the total height of the pavement slab can limit any finishing which adds height.
The paved concrete surface effects environmental parameters to include noise generation induced from traffic traversing the pavement. When set concrete has to be removed and replaced, the removed concrete creates large amounts of waste.
The texture of concrete surfaces has economic impacts. The pavement surface can directly affect tire wear, to include tread and studs. Pavement surfacing effects safety conditions, as well. The pavement surface will impact skid resistance and water drainage. On pedestrian surfaces, the paved surface can effect the safe ride of recreational equipment, such as inline skates. Pedestrian traffic can lead to surface concerns on many paved surfaces, in addition to sidewalks. For example, concrete surfaces may need to be able to accommodate persons using walking assistive devices.
Differences in use, purpose, terrain, and weather can all require different surface types and tolerances. For example, an area designed for skateboarding would have different surface standards than either a pedestrian walkway, or a street. A flat area with high rainfall and high traffic may have different surface tolerances as compared to a gradual slope in an arid environment with very little traffic. Different uses, such as interstate highway, racing track, canal, and aircraft runway, will all have different surface standards.
The surface of the pavement can affect load impact, which in turn can affect the service life of the pavement. Methods to evaluate and correct roadway pavement when the cement is still plastic, able to be reshaped, can have immediate effects, such as skid resistance, and long term effects, such as load impact and road wear. By detecting surface defects before the cement is set, economical and effective surface correction is possible.
Conventionally, cement for large concrete slabs and roadways is laid using a slip-form paver or a fixed form paver. Concrete is poured, smoothed with a trowel, and allowed to cure before inertial surface profile, smoothness, characteristics are measured to assess compliance with surface standards and goals. Irrespective of the type of paving employed, jointed plain (JPCP), jointed reinforced (JRCP) and continuously reinforced (CRCP), surface measurements are conventionally made after the cement has set. FIG. 1 shows a paving train 100 with a spreader 110, followed by a paver 120, which is followed by a finisher 130. The paver 120 shown in FIG. 1 is a conventional slip-form paver. And FIG. 2 shows a conventional walking profiler 200, which is used to make surface measurement and is manually pushed on set cement.
Conventionally, finishers follow behind a paver and perhaps a working bridge, troweling the wet cement to a smooth surface. By identifying bumps or indentations which exceed the desired surface roughness, right after the cement has been laid, finishers can re-trowel the deficient surface with little or no retracing of steps. Corrections could be made with little or no additional labor, operation, or material costs.
Conventional real time bump detectors include those developed by Ames Engineering (Ames Engineering, Ames, Ind., U.S.A.) and Gomaco (Gomaco, Ida Grove, Ind., U.S.A.) The Ames device uses three laser sensors which measure displacements between the wet concrete and a beam extending out from the paving device. However the device has high costs, which include the cost of each laser.
Godbersen et al. (U.S. Pat. No. 7,044,680) uses non-contact, e.g. sound wave reflection, sensors. Discrepancies to include bumps in wet concrete can be identified and estimated using non-contact sensors with a slope sensor, detecting the slope of the sensor beam. The apparatus can be mounted behind a road paving machine to provide real time feedback. The system is not, however, readily attachable to an existing paver, and requires a dedicated expansive rig.
An economical device is desirable for widespread implementation by various pavers and for projects of smaller size, as well. It would be desirable if an apparatus, system, and method could provide bump detection at low cost. It would also be desirable if existing pavers could readily, or be readily modified to, accommodate the bump detector, surface profiler.
In addition to the considerations above, transportation departments may have ride quality and/or surface smoothness criteria for paved roadways. To assist contractors and pavers in meeting or exceeding these surface and ride quality standards, evaluation of the surface quality of wet cement is desirable. For these reasons and those discussed above, a method for early bump detection for use during pavement construction of, e.g. Portland Cement Concrete (PCC), pavements is desirable. If a method to check surface smoothness while paving is available, early detection of non-compliant areas may lead to more cost-effective alternatives for correcting deficiencies.
While existing specifications may stipulate that the cost for correcting deficiencies is to be borne by the contractor, in reality, penalties may be factored into the contractor's bid. Thus, if a method for early bump detection is available for the contractor to use, the reduction in his or her risk could potentially translate to a lower bid with the result that a superior riding pavement is obtained at less cost.
A surface profiler and bump detector would need to be able to withstand the paving environment, which may include vibration, jerking, water spray, and chemicals.
The construction of smooth and durable pavements is a major objective in roadway construction projects. Transportation departments may develop and revise ride quality specifications. When quality assurance is conducted on dry set cement, these specifications may call for remedial action after the concrete has hardened, which is expensive. Then, it may become necessary to grind the concrete, which leaves a permanent scar for the life of the pavement. If early detection of inadequate ride or smoothness in PCC pavements was possible and affordable, corrective measures could be taken before the concrete has hardened. And in turn, a better product at less cost could potentially be achieved.
Paving contractors, flat floor slab contractors, engineers, departments of transportation, Federal Highway Authorities, and Federal Aviation Authorities could all benefit from an economical, accurate, and easy to implement method of surface measurements on wet cement.